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What are the risk factors?

Many factors can increase your risk of breast cancer. But having risk factors does not mean that you will develop breast cancer. For more information, see breastcancerriskfactors.gov.au or petermac.org/iprevent.

personal factors – older age; dense breast tissue as seen on a mammogram.

lifestyle factors – being overweight or gaining weight after menopause; drinking alcohol every day; not being physically active.

medical factors – using menopause hormone therapy (MHT) that contains both oestrogen and progestogen; taking the pill for a long time (small increase); taking diethylstilboestrol (DES) during pregnancy; having radiation therapy to the chest for Hodgkin lymphoma; having atypical ductal hyperplasia or proliferative disease without atypia; previous diagnosis of LCIS or DCIS.

reproductive factors – starting first period younger than 12; being older than 30 at the birth of first child; not giving birth; not having breastfed; going through menopause after 55.

family history factors – a family history of breast cancer and/or a particular type of ovarian cancer in first degree relatives (e.g. mother, sister) on the same side of the family, especially if diagnosed at a young age.

personal factors – older age.

medical factors – a rare genetic syndrome called Klinefelter syndrome – males with this syndrome have three sex chromosomes (XXY) instead of the usual two (XY).

family history factors – a family history, with several first-degree relatives (male or female) who have had BRCA2 breast cancer; a relative diagnosed with breast cancer under the age of 40; or several relatives diagnosed with ovarian, colon or prostate cancer.

Most people diagnosed with breast cancer don’t have a family history of the disease. However, a small number of people may have inherited a gene fault that increases their breast cancer risk. Everyone inherits a set of genes from each parent, so they have two copies of each gene. Sometimes there is a fault in one copy of a gene. This fault is called a mutation or pathogenic variant.

The two most common gene mutations linked to breast cancer are the BRCA1 and BRCA2 genes. Other types include CDH1, PTEN, STK11, TP53, PALB2, ATM and CHEK2. Women in families with an inherited BRCA1 or BRCA2 change are at increased risk of breast and ovarian cancers. Men in families with an inherited BRAC2 change may be at an increased risk of breast and prostate cancers. To find out if you have inherited a gene mutation, you can visit a family cancer clinic. Talk to your doctor or breast cancer nurse.

This information is reviewed by

This information was last reviewed July 2020 by the following expert content reviewers: Prof Bruce Mann, Professor of Surgery, The University of Melbourne, and Director, Breast Tumour Stream, Victorian Comprehensive Cancer Centre, VIC; Dr Marie Burke, Radiation Oncologist, and Medical Director GenesisCare Oncology, QLD; Dr Susan Fraser, Breast Physician, Cairns Hospital and Marlin Coast Surgery Cairns, QLD; Ruth Groom, Consumer; Julie McGirr, 13 11 20 Consultant, Cancer Council Victoria; A/Prof Catriona McNeil, Medical Oncologist, Chris O’Brien Lifehouse, NSW; Dr Roya Merie, Staff Specialist, Radiation Oncology, Liverpool Cancer Therapy Centre, Liverpool Hospital, NSW; Dr Eva Nagy, Oncoplastic Breast Surgeon, Sydney Oncoplastic Surgery, NSW; Gay Refeld, Clinical Nurse Consultant – Breast Care, St John of God Subiaco Hospital, WA; Genny Springham, Consumer.